use fake timers in tests
use fake timers in tests

Summary:
Fake timers was a default that has changed in Jest at some point. This brings us
back in line with the internal config of enabling them by default.

Reviewed By: leebyron

Differential Revision: D4805609

fbshipit-source-id: 1f6d28421aba8f72c8bb334c6ca257491fc8d32a

wincent/relay,kassens/relay,iamchenxin/relay,cpojer/relay,rosskevin/relay,facebook/relay,chentsulin/relay,kassens/relay,facebook/relay,cpojer/relay,cpojer/relay,wincent/relay,kassens/relay,benjaminogles/relay,kassens/relay,xuorig/relay,yungsters/relay,voideanvalue/relay,xuorig/relay,freiksenet/relay,atxwebs/relay,dbslone/relay,voideanvalue/relay,iamchenxin/relay,josephsavona/relay,voideanvalue/relay,chirag04/relay,benjaminogles/relay,josephsavona/relay,voideanvalue/relay,chentsulin/relay,apalm/relay,chentsulin/relay,facebook/relay,wincent/relay,facebook/relay,josephsavona/relay,xuorig/relay,xuorig/relay,zpao/relay,atxwebs/relay,iamchenxin/relay,facebook/relay,yungsters/relay,rosskevin/relay,freiksenet/relay,wincent/relay,apalm/relay,apalm/relay,voideanvalue/relay,atxwebs/relay,wincent/relay,iamchenxin/relay,chirag04/relay,facebook/relay,chirag04/relay,zpao/relay,kassens/relay,voideanvalue/relay,zpao/relay,atxwebs/relay,dbslone/relay,xuorig/relay,wincent/relay,xuorig/relay,cpojer/relay,freiksenet/relay,benjaminogles/relay,yungsters/relay,kassens/relay